On the horizon: News from the frontiers of science.

Polar ice meltdown continues, scientists find source of galactic antimatter, new palm tree's crown is its own undoing.

Arctic Thaw: Icebergs float in this undated image from the Arctic National Wildlife Refuge in Alaska. The Brooks Range is in the distance.

meltdown continues at North and south poles

Polar ice is undergoing significant changes at the top and bottom of the globe. Two new studies are yielding insights into those changes, which have long-term implications for climate and sea level.

In Antarctica, an international team of scientists reports that between 1992 and 2004, the rate at which the continent's icecap is losing mass to the oceans increased by 75 percent. The team notes that while increased snowfall in Antarctica's interior has added mass to the icecap's interior, those gains have been offset by the rate at which the flow of glaciers into the ocean has accelerated. The results appear in the current issue of the journal Nature Geoscience.

Up north, another team has analyzed trends in the all-important "old" ice floating in the Arctic Ocean. Much of the oldest, thickest ice has vanished, replaced with multiyear ice that is only two to three years old. This thinner multiyear ice accounted for 35 percent of multiyear ice in the mid-1980s, the team estimates. It now accounts for 58 percent of the multiyear ice.

If this trend toward younger, more-fragile multiyear ice holds, the team says, we're likely to see more episodes of dramatic summertime ice loss like the record loss that occurred in 2007. The results appear in a recent issue of the journal Geophysical Research Letters.

source of antimatter detected

There's a huge cloud of antimatter at the center of our galaxy, and its source has been one of the enduring mysteries of high-energy astrophysics.

Now astronomers say the antimatter is probably being generated by black holes and neutron stars that have a visible star as a companion. Using a European Space Agency satellite that detects gamma rays, researchers in Europe and the United States mapped the distribution of the galaxy's central gamma-ray cloud. It carries the unique energy signature from collisions between electrons and their antimatter counterparts, positrons. They noted that the cloud's shape was stretched in one direction, relative to the galaxy's core. The distorted portion overlapped a region where scientists have discovered a relatively large number of binary stars with a black hole or neutron star as one companion. The research team suggests that the antimatter is being created as gas from the visible companion falls into the black hole or onto the neutron star.

But the results raise a deeper quandary. Researchers don't know how these odd binary star systems could create enough antimatter to account for the cloud's 10,000 light-year size. Nor have they any idea how the antimatter could spread so widely. The results appear in a recent issue of the journal Nature.

New palm tree's crown is its undoing

A random walk in a remote part of Mada­gascar uncovered a unique species of palm tree that in effect starves itself to death.

The palm, which will get a formal name Thursday in the Botanical Journal of the Linnean Society, vaults to heights of 60 feet. With its 16-foot-wide crown of branches and flowers, the trees can be seen using Google Earth, researchers say. But its crown is its undoing. Once it reaches its full height, the top of the trunk explodes in branches and flowers, which literally drip with nectar and develop into fruit. But this process drains the tree of nutrients. Once it produces fruit, the tree collapses and dies.

The first specimen was discovered by Xavier Metz, who manages a cashew plantation on Madagascar. He and his family were walking in a remote part of the island when they came across the palm. They photographed it and posted it on the Web, where experts at the Royal Botanic Gardens, Kew, in Britain saw it. The palm is similar to species found in Arabia, China, and Thailand. But DNA analysis shows that it's not only a new species, but a unique genus as well. Because of habitat loss, fewer than 100 specimens remain.

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